In circuit systems having different circuits powered by different power supplies, digital signals passing between power supply domains are often level-shifted to change the voltage of the signals to be consistent with the domains. A digital input signal exists in an input domain, in which circuits are powered by a first power supply. A digital output signal exists in an output domain, in which circuits are powered by a second power supply. Level-shifting the digital signals ensures the correct logical values are passed from circuits in the input power supply domain to circuits in the output power supply domain.
In conventional level-shifter circuits, when the power supply voltage of an input domain is insufficient (e.g., in a situation in which the input domain power supply is powered down), the input to the conventional level-shifter may be a floating voltage value. A floating level-shifter input can cause high current leakage from a power supply powering the output domain. For example, if a first circuit powered by a first power supply is configured to pass a digital signal to another circuit powered by a second power supply, the second power supply may suffer high leakage via the level-shifter if the first power supply does not have a sufficient voltage for the first circuit to produce a valid input signal to the second circuit.